The disclosure relates generally to suppressing intermodulation product(s) in a wireless distribution system (WDS), such as a distributed antenna system (DAS) and, more particularly, to reducing power consumption in remote units in the WDS.
Wireless customers are increasingly demanding digital data services, such as streaming video signals. At the same time, some wireless customers use their wireless communications devices in areas that are poorly serviced by conventional cellular networks, such as inside certain buildings or areas where there is little cellular coverage. One response to the intersection of these two concerns has been the use of DASs. DASs include remote units configured to receive and transmit communications signals to client devices within the antenna range of the remote units. DASs can be particularly useful when deployed inside buildings or other indoor environments where the wireless communications devices may not otherwise be able to effectively receive radio frequency (RF) signals from a source.
In this regard, FIG. 1 illustrates distribution of communications services to remote coverage areas 100(1)-100(N) of a wireless distribution system (WDS) provided in the form of a DAS 102, wherein ‘N’ is the number of remote coverage areas. These communications services can include cellular services, wireless services, such RF identification (RFID) tracking, Wireless Fidelity (Wi-Fi), local area network (LAN), and wireless LAN (WLAN), wireless solutions (Bluetooth, Wi-Fi Global Positioning System (GPS) signal-based, and others) for location-based services, and combinations thereof, as examples. The remote coverage areas 100(1)-100(N) may be remotely located. In this regard, the remote coverage areas 100(1)-100(N) are created by and centered on remote units 104(1)-104(N) connected to a head-end equipment (HEE) 106 (e.g., a head-end controller, a head-end unit, or a central unit). The HEE 106 may be communicatively coupled to a signal source 108, for example, a base transceiver station (BTS) or a baseband unit (BBU). In this regard, the HEE 106 receives downlink communications signals 110D from the signal source 108 to be distributed to the remote units 104(1)-104(N). The remote units 104(1)-104(N) are configured to receive the downlink communications signals 110D from the HEE 106 over a communications medium 112 to be distributed to the respective remote coverage areas 100(1)-100(N) of the remote units 104(1)-104(N). In a non-limiting example, the communications medium 112 may be a wired communications medium, a wireless communications medium, or an optical fiber-based communications medium. Each of the remote units 104(1)-104(N) may include an RF transmitter/receiver and a respective antenna 114(1)-114(N) operably connected to the RF transmitter/receiver to wirelessly distribute the communications services to client devices 116 within the respective remote coverage areas 100(1)-100(N). The remote units 104(1)-104(N) are also configured to receive uplink communications signals 110U from the client devices 116 in the respective remote coverage areas 100(1)-100(N) to be distributed to the signal source 108. The size of each of the remote coverage areas 100(1)-100(N) is determined by the amount of RF power transmitted by the respective remote units 104(1)-104(N), receiver sensitivity, antenna gain, and RF environment, as well as by RF transmitter/receiver sensitivity of the client devices 116. The client devices 116 usually have a fixed maximum RF receiver sensitivity, so that the above-mentioned properties of the remote units 104(1)-104(N) mainly determine the size of the respective remote coverage areas 100(1)-100(N).
With reference to FIG. 1, each of the remote units 104(1)-104(N) may be configured to support more than one type of wireless service that operates in a variety of RF spectrums and bandwidths. The downlink communications signals 110D received by the remote units 104(1)-104(N) are typically amplified by a power amplifier to increase signal strength before distributing the downlink communications signals 110D to the client devices 116 through the respective antenna 114(1)-114(N). However, non-linearity of the power amplifier can cause an intermodulation product(s) (e.g., a third-order intermodulation product (IM3), a fifth-order intermodulation product (IM5), etc.) to be generated when the power amplifier amplifies the downlink communications signals 110D. For instance, when the downlink communications signals 110D operating in a 850-870 megahertz (MHz) downlink spectrum are amplified by the power amplifier, intermodulation product(s) may be generated below 850 MHz (e.g., 830 MHz, 810 MHz, 790 MHz, and so on) and above 870 MHz (e.g. 890 MHz, 910 MHz, 930 MHz, and so on). The intermodulation product(s) may leak from a downlink signal path 118D into an uplink signal path 118U in the remote units 104(1)-104(N) if the downlink signal path is insufficiently isolated from the uplink signal path. As a result, the leaked intermodulation product(s) may interfere with the uplink communications signals 110D that are received in an adjacent uplink spectrum. For example, if a remote unit 104(1)-104(N) receives the uplink communications signals 110U in an 825-845 MHz uplink spectrum, the intermodulation product generated at 830 MHz would fall into the 825-845 MHz uplink spectrum, thus interfering with the uplink communications signal 110U. As such, it may be desirable to suppress the intermodulation product(s), which may be leaked from the downlink signal path into the uplink signal path, to reduce RF interference and improve RF performance in the remote units 104(1)-104(N).
No admission is made that any reference cited herein constitutes prior art. Applicant expressly reserves the right to challenge the accuracy and pertinency of any cited documents.